Extracellular heat shock proteins (HSP) have been shown to have a profound effect on tumor immunity. We have prepared a highly effective cancer vaccine by extracting Hsp70/Hsp90 complexes from the fusion of tumor cells and dendritic cells (Hsp70.PC-F). We aim in this proposal to examine the properties of the vaccine and optimize its use either solo or combined with ionizing radiation. We aim first to understand the role of the receptor SRECI in dendritic cells (DC) in binding to Hsp70.PC-F and subsequent uptake and presentation of antigens to T lymphocytes. We aim to determine how SRECI can orchestrate antigen cross presentation, innate immune stimulation and cell regulation in DC. Next, in the translational studies in Aim 2 we will examine the role of Hsp70.PC-F in treatment of spontaneous mammary carcinoma in mice. We aim to determine treatment effectiveness and the degree to which vaccines can be used in combination with adjuvants such as TLR3 and TLR9 agonists as well as inhibitors of co-repressing molecule CTLA4. We will further determine whether vaccine design can be manipulated to give selective destruction of tumor initiating cells and radiation resistant cells that accumulate in fractionated radiation therapy.